Shower & Bathtub Waterproof Finish (NBC 9.29.2)

The requirement

The National Building Code doesn’t set one waterproofing height for a bathroom. It sets three, and which one applies depends on the fixture (NBC 2020, Division B, Article 9.29.2.1 “Waterproof Wall Finish — Where Required”):

Fixture	Waterproof finish required to
Shower stall	At least 1.8 m above the floor
Bathtub fitted with a shower	At least 1.2 m above the rim
Bathtub not fitted with a shower	At least 400 mm above the rim

A shower stall gets the tallest wall — 1.8 m — because it’s the wettest spot in the room. A bathtub with a shower head over it sits lower, at 1.2 m above the rim. A tub with no shower at all only needs the splash-zone height, 400 mm above the rim.

NBC 2020 · 9.29.2

1 shower floor
2 basin / bath

What counts as a waterproof finish, and what backs it

Article 9.29.2.2 names the materials that satisfy the waterproof-finish requirement: ceramic, plastic or metal tile, sheet vinyl, tempered hardboard, laminated thermosetting decorative sheets, or linoleum. Plain painted drywall doesn’t qualify on its own.

If you’re tiling, there’s a backer rule too. Article 9.29.10.4 requires ceramic and plastic tile on walls around bathtubs or showers to be applied over moisture-resistant backing — not bare gypsum board. And where the tile meets the bathtub itself, Article 9.29.10.5 requires that joint to be caulked with a mildew-resistant sealing compound conforming to CAN/CGSB-19.22-M.

Neither of these articles specifies a sheet or liquid membrane behind the backing — the NBC’s wording stops at “waterproof finish” and “moisture-resistant backing.” Product-level membrane systems sit with manufacturer instructions and standards like the CSA A123 series, not written into these clauses as a mandatory layer.

On site — what to check

Read the fixture, not just the room. A shower stall needs 1.8 m; a bathtub with a shower needs 1.2 m above the rim; a plain bathtub only needs 400 mm above the rim.
Pick a listed finish — tile, sheet vinyl, tempered hardboard, laminated thermosetting sheet or linoleum — up to the required height.
Back the tile properly. Moisture-resistant backing behind tile around any bathtub or shower, not plain gypsum board.
Caulk the tub-to-tile joint with a mildew-resistant sealant conforming to CAN/CGSB-19.22-M.
Check your province. Confirm the edition and any local amendments with your building department before you build.

Part of the Canada building codes hub — how the NBC is adopted province by province.
Building the room around it? See Canada minimum ceiling heights — the 2.1 m rule for bathrooms and laundries.
Setting the shower floor slope and drain is a plumbing job — check with your plumber and the locally adopted plumbing code.

Sources

NBC 2020, Division B, Section 9.29 “Interior Wall and Ceiling Finishes,” Article 9.29.2.1 “Waterproof Wall Finish — Where Required” and Article 9.29.2.2 “Materials” — the 1.8 m / 1.2 m / 400 mm heights and the listed waterproof-finish materials. Free official PDF via nrc-publications.canada.ca (National Building Code of Canada 2020, Volume 2). (Confirmed by direct text extraction from the official NRC PDF, verified 2026-07-31.)
NBC 2020, Article 9.29.10.4 “Moisture-Resistant Backing” and Article 9.29.10.5 “Joints between Tiles and Bathtub” — the tile-backer requirement and the CAN/CGSB-19.22-M caulking requirement at the tub-to-tile joint. Same source and verification as above. (Note: Article 9.29.10 itself is titled “Wall Tile Finish” and covers tile installation method — mortar base, adhesives, backing, joints. The waterproof height figures come from the separate Article 9.29.2, not 9.29.10.)
Adoption caveat: The National Building Code is a model code with no legal force of its own — it binds you only once your province or territory adopts it, often with amendments. Ontario runs the Ontario Building Code, Québec its own construction code, and British Columbia the BC Building Code, each with different numbering and, in places, different figures. Always confirm the edition in force where you build.

Frequently asked questions

How high does a shower wall have to be waterproofed in Canada?

Under the National Building Code, a shower stall needs a waterproof finish up to at least 1.8 m above the floor. That figure sits in NBC 2020, Article 9.29.2.1, the 'Waterproof Wall Finish' provision in the interior finishes section.

What about the wall above a bathtub?

It depends on whether the tub has a shower. Above a bathtub fitted with a shower, the waterproof finish has to reach at least 1.2 m above the rim. Above a bathtub with no shower, it only has to reach 400 mm above the rim — a lower splash-zone height, not a full shower wall.

What materials count as a waterproof finish under the NBC?

Article 9.29.2.2 lists ceramic, plastic or metal tile, sheet vinyl, tempered hardboard, laminated thermosetting decorative sheets, or linoleum. Plain gypsum board on its own doesn't qualify.

Does tile need a special backer behind it?

Yes. NBC 2020 Article 9.29.10.4 requires ceramic and plastic tile on walls around bathtubs or showers to be applied over moisture-resistant backing — not plain gypsum board. The joint between the wall tile and the bathtub itself also has to be caulked with a mildew-resistant sealing compound conforming to CAN/CGSB-19.22-M (Article 9.29.10.5).

Do these NBC figures apply everywhere in Canada?

Not automatically. The NBC is a model code with no legal force on its own — it binds you only once your province or territory adopts it, and several publish their own code instead. Ontario runs the Ontario Building Code, Québec its own construction code, and British Columbia the BC Building Code, each with its own numbering and sometimes different figures. Confirm the edition in force where you build.